The present invention relates to a solid catalyst component and catalyst for polymerization of a propylene, which shows a high activity and an excellent hydrogen response, and further, can provide a polymer having a high stereoregularity in a high yield.
A solid catalyst component containing magnesium, titanium, an electron donor compound and halogen as essential components has been known as a catalyst component for polymerization of a propylene. Many proposals have been made and known for a process for the polymerization or the copolymerization of a propylene in the presence of a catalyst for polymerization of a propylene comprising said solid catalyst component, an organic aluminum compound and an organic silicon compound. For example, JP-A-57-63310 and JP-A-57-63311 (The term xe2x80x9cJP-A as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) propose processes for polymerizing an olefin having a carbon number of more than 3 by using a catalyst system comprising a solid catalyst component containing a magnesium compound, a titanium compound and an electron donor compound, an organic aluminum compound and an organic silicon compound having Sixe2x80x94Oxe2x80x94C bond. However, these processes are not always satisfactory for obtaining highly stereoregular polymers in a high yield, and further improvement has been demanded.
On the other hand, JP-A-63-3010 discloses a catalyst system for the polymerization of a propylene and a process for polymerizing a propylene using the same, the catalyst system comprising a solid catalyst component prepared by bringing a dialkoxymagnesium, a diester of an aromatic carboxylic acid, an aromatic hydrocarbon and a titanium halide into contact and subjecting the resulting product in a powdered state to a heat treatment, an organic aluminum compound and an organic silicon compound.
JA-A-1-315406 discloses a catalyst system for polymerizing a propylene comprising a solid catalyst component prepared by bringing a titanium tetrachloride into contact with a suspension formed by a diethoxymagnesium with an alkylbenzene, adding phthalic dichloride thereto to react to obtain a solid product, and further contacting the resulting solid product with a titanium tetrachloride in the presence of an alkylbenzene, an organic aluminum compound and an organic silicon compound, and a process for polymerizing a propylene in the presence of said catalyst system.
The foregoing known techniques focus on the development of a catalyst component having a high activity enough to allow the omission of a so-called deashing step, i.e., step of removing catalyst residues such as chlorine and titanium remaining in the polymer produced as well as on the enhancement of the yield of stereoregular polymer or an improvement in durability of the catalyst activity for polymerization, and achieved excellent results to these purposes.
The propylene polymer obtaining by using the foregoing catalysts is utilized in various uses, e.g., a container or a film other than a molded product of an automobile or household appliances. When products are molded with many kinds of molding machines from a fused polymer powder produced by polymerization, especially when large molded products are manufactured by the method such as an injection molding, etc. a high melt flow rate of the fused polymer is demanded. Therefore, many researches have been conducted to advance a melt flow rate of a polymer.
A melt flow rate of a polymer is very dependent on a molecular weight of the polymer. In manufactory industries, hydrogen is generally added as a regulator of a molecular weight of a polymer produced in the polymerization of a propylene. In order to produce a polymer having a low molecular weight, i.e, in order to produce a polymer having a high melt flow rate, a lot of hydrogen is usually added, but a quantity of hydrogen can be added is limited because a pressure-resistance of a reactor is limited for safety. Therefore a partial pressure of a monomer should be reduced in this case, so that a productivity of a polymer should be declined. Also a problem of a cost arises from using a large quantity of hydrogen. So the development of a catalyst system which shows a high hydrogen response, which can provide a polymer having a high stereoregularity in a high yield, and which can produce a polymer having a high melt flow rate even when a quantity of hydrogen used in polymerization is little is demanded, but the foregoing known techniques have been not enough to resolve the problems.
Furthermore, because compounds each having a benzene ring have been mainly used as an electron donor compounds in foregoing known techniques, the present inventors have evaluated compounds each having no benzene ring as electron donor compounds in view of the environmental issue. Therefore, the present inventors have found that some kinds of derivatives of maleic acid show an excellent effect and reached to the completion of the present invention.
As a result of extensive investigations to solve the foregoing problems remaining in the prior art techniques, the present inventors have found that to use a diester of maleic acid each having a straight-chain or branched chain alkyl groups having a carbon number of 2 to 8 among all kinds of a diester of maleic acid as a principal component of an electron donor, and particularly to use at least one species of a diester of maleic acid each having a straight-chain alkyl groups having a carbon number of 2 to 5 as a principal component of the diester of maleic acid are very effective to solve the problems. Therefore the present inventors have reached to the completion of the present invention.
Namely, an objective of the present invention is to solve the problems remaining in the prior art techniques and to provide a solid catalyst component and a catalyst for polymerization of a propylene, which shows a higher hydrogen response and a higher activity than that of a conventional catalyst, can provide a polymer having a high stereoregularity and a high bulk density in a high yield, and contains no aromatic esters as constituent components.
To solve the objective of the present invention, a solid catalyst component for polymerization of a propylene of the present invention is prepared by bringing a dialkoxymagnesium (a), a tetravalent halogen-containing titanium compound (b), and a diester of maleic acid each having a straight-chain or branched-chain alkyl group having a carbon number of 2 to 8 (c) into contact with one another. In the procedure a diester of maleic acid each having straight-chain alkyl group having a carbon number of 2 to 5 may be used preferably as a principal component of the component (c). Furthermore, the solid catalyst component for polymerization of a propylene of the present invention may be prepared preferably by contacting the foregoing components with one another in a suspended state in an aromatic hydrocarbon (d) which boiling point is from 50 to 150xc2x0 C.
Further a catalyst system for polymerization of a propylene of the present invention comprises:
(A) the foregoing solid catalyst component,
(B) an organoaluminium compound represented by the general formula (1):
R1pAlQ3xe2x88x92pxe2x80x83xe2x80x83(1)
wherein R1 represents an alkyl group having a carbon number of 1 to 4, Q represents a hydrogen atom or halogen atom; and p represents a real number of from more than 0 to not more than 3; and
(C) an organic silicon compound represented by the general formula (2)
R2qSi(OR3)4xe2x88x92qxe2x80x83xe2x80x83(2)
wherein R2 represents an alkyl group having a carbon number of 1 to 12, cycloalkyl, phenyl, vinyl, allyl or aralkyl group which may be the same or different; R3 represents an alkyl group having a carbon number of 1 to 4, cycloalkyl, phenyl, vinyl, allyl or aralkyl group which may be the same or different; and q represents 0 or an integer of from 1 to 3.